1. Field of the Invention
This invention relates to a cutter wheel for use in cutting a work piece material such as concrete, and more particularly to a rotary cutting wheel having cutting bits, which is capable of spontaneously producing a strong current of air when being rotated for cutting a rigid material so as to cool effectively the cutting bits.
2. Description of the Prior Art
For the purpose of cutting rigid materials such as concrete, asphalt, brick, tiles and stone, there has been generally used a rotary cutter wheel, comprising a cutter base having a substantially disc shape and at least one cutting bit which is formed by shaping and sintering ultrahard abrasive grains including diamond grains or the like and attached to the peripheral portion of the cutter base by silver soldering. When cutting such a rigid material with the cutter wheel of this type, superheat is generated due to friction between the cutting bit and the rigid material. The frictional heat generated in cutting the rigid material increases remarkably the wear rate of the cutting bit, to thereby decrease the lifetime of the cutting blade.
To prevent the cutting bit of the cutter wheel from reaching a high temperature in cutting, there have conventionally been employed various method for cooling the cutting bit by forcing water or air to spout from the circumferential part of the cutter wheel towards the cutting bit. A conventional water-cooling method using water as coolant has an effect of sufficiently cooling the cutting bit, whereas it entails a disadvantage in that the material to be cut and the circumferences thereof are considerably stained with the water spouted from the cutter wheel. If a hood cover encircling the cutter wheel is used for recovering the water spouted from the cutter wheel, it adds to the size and complexity of the cutter device and renders the handling of the device difficult.
As one example of an air-cooling method using air as a coolant for the cutting bit, Japanese Utility Model Appln. Public Disclosure SHO 64-42110(A) describes a device in which air is compulsorily introduced into interior air passages formed radially in the cutter base and sent out from the outer peripheral part of the cutter wheel. This forced air-cooling method requires an air supplying system including an air compressor and an air supplying pipe, and therefore, it limits the handling of the cutting device.
Thus, it may be envisaged that a separate air introducing fan is attached to the outside of a rotary cutter wheel having a plurality of interior air passages formed radially so as to permit air introduced into the air passages by the fan attached to the wheel when rotating the wheel to spout out from the peripheral part of the cutter wheel towards one or more cutting bits mounted on the circumferential part of the wheel. To carry out the idea mentioned above, there may be used a cutter wheel having radial air slots as proposed in U.S. Pat. No. 3,049,843 and Japanese Utility Model Appln. Public Disclosure SHO 64-42110(A).
However, such a cutter wheel having the aforesaid structure is not practical from the viewpoint of productivity and handling. That is to say, the cutter device using such a fan built-on type cutter wheel which comprises a plurality of air passages formed radially in the wheel base thereof and the aforenoted separate fan attached to the outside surface of the wheel base is disadvantageous in that it is bulky and requires labor for its assembly. Besides, this cutter wheel entails problems such as decrease in rotating performance due to the imbalance thereof and difficulty in forming the air passages of small diameter within the wheel base.
Furthermore, in the cutter wheel of this type having one or more cutting bits attached to the cutter base and formed of ultrahard abrasive grains including diamond grains or the like, the cutting bits must be fixedly placed at the prescribed positions on the peripheral portion of the cutter base with a high accuracy. If the longitudinal center of the cutting bit does not exactly coincide with the circumferential center of the cutter base, the cutter wheel rotates and causes wobbling and vibration to decrease the rotating performance of the cutter wheel and may cause the cutting bit to break.